Carbon contact for telephones



, currents, 83c.

UNITED STATES JOHN H. IRWIN, OF MORTON, PENNSYLVANIA.

CARBON CONTACT FOR TELEPHONES.

SPECIFICATION forming part of Letters Patent No. 238,784, dated March 15, 1881.

Application filed January .19, 1881.

To all whom it may concern:

Be it known thatI, JOHN H. IRWIN, of Morton, Delaware county, Pennsylvania, have invented a new and useful Improvement in Carbon Contacts and Buttonsfor'Telephone or Microphone Transmitters, of which the following is a specification.

My invention relates to a method of treating the carbon button s or contacts of a batterytraiismitter with a view to eliminating, so far as may be, the crackling or sputtering noises that accompany the transmission of articulate sounds and interfere with the distinctness ot' the received articulations, and that are in all cases a source of annoyance. These foreign and disturbing sounds have been attributed to many causes, such as disturbance in the electrical conditions of the atmosphere, earth- My observations and experiments have led me to believe that they are in large measure due, where battery or contact transmitters are used, to the electrical decomposition of aqueous vapor or moisture, which, by reason of the structural nature of the carbon, is present in its pores or interstices, to a greater or less degree dependent upon the hygrometric condition of the surrounding atmosphere, and that the disturbing cause-is, in fact, the sudden liberation of constituent gases by electrolysis.

In order to remove this source of annoyance and confusion in the reception of the transmitted sounds, I have conceived the idea of moistening or saturating the carbon with a liquid or material not readily decomposable by the action of the electric current, but WlllGll will exclude aqueous vapor or mo1sture from the body or pores of the carbon without interfering with its proper action as a tensionchanger. To accomplish this ob ect I moisten or saturate the ca l on with a non-conducting liquid or substance, such as petroleum ormineral hydrocarbon, animal or vegetable oils or r narafiine. l ya ioiis methods may be adopted tor applyin g the non conducting substance. Where such substance is a liquid 1t 1s snnply necessary to heat the carbon to a sufficlent degree to expel any aqueous moisture, and then ap- (No model.)

ply the liquid by pouring it over the carbon, or by dipping the carbon into it.

I have obtained excellent results by the application ot'ordinary petroleum. It is, ot'course, desirable in all cases that the non-conducting substance should be as free as possible from acids, or any material that would be readily decomposable, or would attack the metallic contact-points ordinarily used in conjunction with carbon buttons. A carbon button treated in this way may be used in any form of batterytransmitter, and is applicable not only to those forms in which metallic electrodes are used in contact with the carbon, but also to those in which both contacts are of carbon. \V hen such non-conducting liquid is of a fatty or oily nature, as is ordinarily thecase,itactsto prevent the secretion or absorption of moisture by its repellent action, as well as by filling the pores or interstices of the button.

This method of treating carbon buttons may obviously be applied to other resistance-contacts, which, by reason of their structural nature, may absorb or hold aqueous vapors or moisture; and I contemplate, therefore, applying the same treatment to resistance-pieces formed of finely-divided metals or conductors compacted into shape in any suitable manner, as well as to any other contact piece or resistance whose structure is in any degree porous.

As an additional result flowing from the use of a carbon contact treated in the manner above described, I have-found that the point of the metallic electrode is less liable to become oxidized, and that theinstrument is more DRAFTSMAN constant in its action and less liable to get out of adjustment.

I do notwish to be understood as limiting myself to the particular non-conductingdiq; .7

contact treated or saturated with a non-con- 4. A carbon resistance-piece moistened 0r ducting substance or ltYiiiET. saturated with petroleum, substantiullyns and to a) v 1 J. I A catiitn jgnttcn 01 contact IGblhtflHCO to! the DHIPO-SO dencubed. moistened 01' treated \vitiifirmm cfi'imficting .1. H. IRWIN. 5 substanccoriiquithau-bstantial1yasdescribctl. Witnesses:

3. A carbon i c's (3611i cc moistened or II. (J. TOWNSEND,

trcatcd'Wit-h a 11511fticiu'bcii iiqnid or sub- JOHN J. DIFFLEY.

stance. 

